Abstract
An appraisal of population processes in the Colorado potato beetle, Leptinotarsa decemlineata (Say), on its principal host plant showed that the insect has no natural agents that act in a manner that prevent it from overshooting its food supply. It is little affected by weather conditions or predators, and its only parasite, the tachinid Doryphorophaga doryphorae (Riley), is inversely density dependent in its action. Once the beetle has exploited its food resource, the larvae starve and the adults emigrate in quest of other hosts.The analysis of age interval survivals showed that populations are both regulated and disturbed by the principal key factor, adult migration, which is density dependent but overcompensating. A predictive model based on density relationships explained 94% of the variance in population trend.